I was reading In a Land Before Dev Tools by Amber, and I thought, Oh here missing in the history the beautifully chiseled Opera Dragonfly and F12 for Internet Explorer. So let's see what are all the things I myself didn't know.

(This is slightly larger than just browser devtools, but close from what the web developers had to be able to work. If you feel I had a glaring omission in this list, send me an email kdubost is working at mozilla.com)

• 1997-12: JavaScript debugger for Netscape Communicator, future Firefox. (JavaScript Debugger)
• 1998-02: Microsoft Script Debugger for IE 4.0. Thanks to Kilian Valkhof (added on 2020-08-07)
• ~2001: DOM Inspector in Mozilla code base.
• 2001-10: Venkman, JavaScript debugger inside Mozilla Suite by Robert Ginda. (Venkman)
• 2003-10: Fiddler for IE for understanding HTTP network issues (History of releases)
• 2005-09: Developer Toolbar for IE. (Developer Toolbar for IE announced at PDC) which later on became F12
• 2006-01: Firebug for Firefox by Joe Hewitt as an extension for Firefox. Probably 2005, but the first release is January 2006. (11 years of history)
• 2006-01: Web Inspector for Safari. (Introducing the Web Inspector and 10 Years of Web Inspector)
• 2006-06: Drosera for Safari, JavaScript debugger (Introducing Drosera)
• 2007-07: Yslow made by Yahoo! for Firebug originally. It analyzed the pages for its performances. (YSlow Release on YDN)
• 2008-05: Opera Dragonfly in… Opera. Died in 2012 when the company decided to switched to Blink. Sniff. One of the best debugging tools at the time. Opera Dragonfly homepage
• 2008-09: DevTools in Chrome (10 years anniversary post)
• 2009-06: PageSpeed, a tool to evaluate the performance of the Web page, similar to Yslow. (Introducing Page Speed)
• 2009-07: Opera Scope Protocol initially proposed to have a common protocol for all devtools. Browser implementers decided that they were not interested to converge. Opera Scope Protocol Specification Released
• 2009-10: HTTP Archive Specification, a format for HTTP monitoring tools.
• 2010-02: Firebug Lite for Chrome

Note: Without WebArchive, all this history would not have been possible to retrace. The rust of the Web is still ongoing.

Otsukare!